MACRO TO MICRO POROUS CERAMIC AND CARBON MEDIA – PHILOSOPHY OF DESIGN AND FABRICATION CHEN XINWEI B. Eng. (Hons.), NUS A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMICAL AND BIOMOLECULAR ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2012 Declaration Page DECLARATION I hereby declare that the thesis is my original work and it has been written by me in its entirety. I have duly acknowledged all the sources of information which have been used in the thesis. This thesis has also not been submitted for any degree in any university previously. Chen Xinwei 25 October 2012 i|Page Acknowledgements Acknowledgements First and foremost, I would like to express my sincere gratitude to my supervisor, Associate Professor Hong Liang for his invaluable guidance and advice, remarkable encouragement and continuous support throughout my PhD project, without whom the work will not be achieved. Prof. Hong’s uncompromising and prudent attitude towards research has influenced me deeply. His cheerful, approachable nature and dedication to work and students is widely shared and deeply admired. Special mention also goes to Prof. Chung, Tai-Shung and Dr. Liu Zhaolin for providing me the opportunities and necessary support to showcase my research to the scientific world, both locally and internationally. I would also like to thank my colleagues, Mr. Sun Ming, Dr. Liu Lei, Dr. Guo Bing, Mr Zhao Xiangcheng, Ms. Aklima Afzal, Mr. Zhou Yi’en, Mr. Chen Fuxiang, Ms. Wang Haizhen, Dr. Gong Zhengliang and Dr. Yin Xiong for their friendship and support during my time PhD course. Particular thanks go to Mr. Ng Kim Poi for providing help and advice on the fabrication and design of experimental apparatus. I would like also like to thank my FYP students who have contributed to my research. They include: Ms. Chen Xinling, Mr. Lee Chin Yong, Mr. Tai Xiaohua, Mr. Au Yeong Wen Hao, Ms. Chan Wan Ki Isabel, Ms. Lim Qing Yue Janice, Ms. Phua Ji Ying Rina, Mr. Ong Zheng Wei Benjamin, Mr. Kim Min Woo, Ms. Lim Jia Fang, Mr. Khoo Kian Guan and Mr. Tan Ming En Benjamin. I would like to thank the laboratory staff: Ms Yanfang, Ms Alyssa Tay, Ms Sandy, Mr. Alistair Chan and Mr. Ang Wee Siong for their care and ever-readiness to assist. I’m also extremely grateful to by beloved family members for their love and support throughout the time of the PhD course. I would like to thank my fiancée, Ms. Tan Yan Yan for ii | P a g e Acknowledgements her understanding and patience. I thank God for them and their unconditional love, understanding and I would like to give praise to HIM for whatever I have achieved. Finally, I would like to thank all the staff in National University of Singapore (NUS), Institute of Material Research and Engineering, Singapore (IMRE) and NRF grant (R279-000261-281) for supporting my research work. iii | P a g e Table of Contents Table of Contents Declaration Page i Acknowledgements . ii Table of Contents . iv Summary xii Abbreviation xv List of Figures . xxi List of Tables xxxvi Chapter : Introduction 1.1 Motivation and Overview 1.2 Research Objectives 1.3 Structure of thesis Chapter : Background and Theory for Porous Ceramics 12 2.1 Introduction to Ceramics . 13 2.2 Overview of ceramic fabrication technology 13 2.3 Powder processing – role of additives in consolidation . 15 2.3.1 Solvents . 15 2.3.2 Dispersants 16 2.3.3 Binders 17 2.3.4 Plasticizers 19 2.4 Forming techniques for green body . 21 2.4.1 Pressing . 21 2.4.1.1 Die Pressing 21 2.4.1.2 Isostatic Pressing . 22 2.4.2 Casting methods 23 iv | P a g e Table of Contents 2.4.2.1 Slip casting 24 2.4.2.2 Tape casting 25 2.4.3 2.5 Sol-gel processing and gel-casting 25 Sintering – Grain growth, pore evolution and its thermodynamics 29 2.5.1 Grain growth . 29 2.5.2 Thermodynamics of sintering . 29 2.5.3 Pore evolution . 31 2.6 Macro-porous ceramic forming techniques . 33 2.6.1 Replica technique 34 2.6.2 Sacrificial template method . 36 2.6.3 Direct foaming method . 37 Chapter : Background and Theory for Carbon Membrane 39 3.1 Introduction . 40 3.2 General preparation of carbon membrane . 41 3.3 Selection of polymeric precursors 43 3.3.1 Polyimides and its derivatives . 43 3.3.2 Phenolic resin 45 3.3.3 Polyfurfuryl alcohol 46 3.3.4 Polyacrylonitrile 47 3.4 Pyrolysis process . 49 3.5 Transportation mechanism in CMS membrane . 53 3.5.1 Viscous flow . 54 3.5.2 Knudsen Diffusion 54 3.5.3 Surface Diffusion 55 3.5.4 Molecular Sieving . 55 3.6 Carbon molecular membrane performance for gas separation . 57 3.6.1 Robeson Plot . 57 3.6.2 Important gas separation for carbon membrane 58 v|Page Table of Contents Chapter : An In-Situ Approach to create Porous Ceramic Membrane: Polymerization of Acrylamide in a Confined Environment 60 4.1 Introduction . 61 4.2 Experimental . 64 4.2.1 Preparation of YSZ particles with polymer binder . 64 4.2.2 Fabrication of YSZ pellets and in-situ solid state polymerization 65 4.2.3 Fabrication of sintered porous ceramics – heat treatment process 66 4.2.4 Characterization of the polymerization process 66 4.2.4.1 Investigation of polymerization heat of acrylamide in the green pellet 66 4.2.4.2 Analysis of polyacrylamide formed in the YSZ green pellets 67 4.2.5 4.3 Characterization of the sintered ceramics pellets 67 4.2.5.1 Porosity, pore size distribution and micro-pore structures 67 4.2.5.2 Gas permeation test . 68 4.2.5.3 Measurement of modulus of rupture – 3-point bending test . 69 Results and Discussion 70 4.3.1 Polymerization in the confinement environment 70 4.3.2 Microstructure created by the polyacrylamide formed in-situ 76 4.3.3 Correlation of gas permeability and modulus of rupture with pore-forming history . 81 4.4 Conclusions . 86 Chapter : Submicron Scale Exclusion via Polymerizing an Aromatic Nylon in Molded Ceramic Monolith for Paving Interconnected Pore Channels 87 5.1 Introduction . 88 5.2 Experimental . 91 5.2.1 Coating YSZ particles with the two monomers 91 5.2.2 Fabrication of YSZ pellets and in-situ solid state polymerization 91 5.2.3 Fabrication of the sintered porous YSZ pellets via carbonization and incineration steps . 92 5.2.4 Characterizations . 93 5.2.4.1 Pellets after polymerization and sintering . 93 vi | P a g e Table of Contents 5.2.4.2 5.3 Fluid flow behavior . 95 Results and Discussion 96 5.3.1 Generation of PPTA nano crystallites in YSZ green pellet 96 5.3.2 Porous features of the sintered YSZ bulk phases 101 5.3.3 Gas permeability test . 108 5.3.4 Rheological response of polymer solution to passing pore channels 110 5.4 5.3.4.1 Permeation-caused thinning effect of dilute PMMA-PVDF solution . 110 5.3.4.2 Verifying the extrusion-induced chain stretching effect . 113 Conclusions . 115 Chapter : Evolution of Throttle-Channel Dual Pores in YSZ Ceramic Monolith through in-situ Grown Nano Carbon Wedges . 116 6.1 Introduction . 117 6.2 Experimental . 120 6.2.1 Fabrication of green body containing in-situ generated PPTA rods . 120 6.2.2 Formation of crystallized carbon rods in the green disc before sintering . 120 6.2.3 Structural characterizations . 121 6.3 Results and Discussion 124 6.3.1 Pore structure evolution with the assistance of nano carbon wedges 124 6.3.2 Influences of pore forming on interconnectivity and flexural strength of YSZ discs . 137 6.3.3 Effects of the locations of carbon porogens on interconnectivity of pore channels . 140 6.3.4 Rheological response due to stretched flow 144 6.4 Conclusions . 147 Chapter : Ceramic Pore-Channels with Inducted Carbon-nanotubes for Removing Oil from Water . 148 7.1 Introduction . 149 7.2 Experimental . 154 7.2.1 Preparation of the CNTs-tailored ceramic membrane . 154 7.2.2 Microscopic and surface area examinations of the CNTs-tailored ceramic vii | P a g e Table of Contents membranes 155 7.2.3 Preparation and quantification of o/w emulsion . 155 7.2.4 Permeation measurements and restoring performance of spent membrane 157 7.3 Results and Discussion 159 7.3.1 Growth of CNTs in YSZ membrane . 159 7.3.2 Removal of oil from o/w emulsions by the CNTs-tailored YSZ membrane . 163 7.3.3 Enhancing size-exclusion separation selectivity by implementing CNT grids . . 168 7.4 Conclusions . 173 Chapter : Performance of Emulsified Oily Water Treatment by Carbon Nanotubes modified Ceramic Pore Channel . 174 8.1 Introduction . 175 8.2 Experimental . 178 8.2.1 Fabrication of porous ceramic membrane . 178 8.2.2 Carbon nano-tube growth in pore channels of ceramic . 178 8.2.3 Oily water filtration test 179 8.3 Results and Discussion 181 8.3.1 Oil concentration . 181 8.3.2 Operating pressure 186 8.3.3 Concentration of surfactant . 188 8.3.4 Type of surfactant . 192 8.3.5 Operating temperature . 194 8.3.6 Membrane porosity . 196 8.4 Conclusions . 202 Chapter : Aliphatic Chain Grafted Polypyrrole as a precursor of Carbon Membrane – effects of the soft side chains 203 9.1 Introduction . 204 9.2 Experimental . 207 9.2.1 Synthesis of the grafted polypyrrole (PPy-DBSA) . 207 9.2.2 Fabrication of carbon membrane 207 viii | P a g e Table of Contents 9.2.3 9.3 Characterization results . 209 Results and Discussion 213 9.3.1 Cause of defect occurrence in carbon membrane: the π-stacking of conjugated chains 213 9.3.2 Grafting of linear segment to polypyrrole . 214 9.3.3 Fabrication of carbon membrane on a porous ceramic substrate 217 9.3.4 Achieving meso-porous carbon membrane: sealing of pinholes . 220 9.4 Conclusions . 226 Chapter 10 : Carbon Nanotubes as Structural Pillars and Micro-porosity Injectors for enhancing Carbon Membrane Performance . 227 10.1 Introduction . 228 10.2 Experimental . 230 10.2.1 Synthesis and application of phenol-formaldehyde prepolymer solution . 230 10.2.2 Synthesis and application of m-cresol layer 231 10.2.3 Synthesis and application of final layer 231 10.2.4 Carbon membrane synthesis with carbon nanotube anchorage . 232 10.2.5 Carbon membrane synthesis with n-methyl-2-pyrrolidone (NMP) 233 10.2.6 Characterizations . 233 10.3 Results and Discussion 234 10.3.1 Application of phenol-formaldehyde prepolymer as prime layer . 234 10.3.2 Incorporation of carbon nanotubes in carbon molecular sieve . 240 10.3.3 Effect of pyrolysis temperature on carbon membrane 244 10.4 Conclusions . 247 Chapter 11 : The Structural Evolution of side-chain grafted Polypyrrole to Carbon Membrane . 248 11.1 Introduction 249 11.2 Experimental . 252 11.2.1 Synthesis of the doped polypyrrole PPy-DBSA . 252 11.2.2 Characterization of PPy and PPy-DBSA derived nanoporous carbon 252 11.3 Experimental Results 254 ix | P a g e References [243] Adhikari S, Fernando S. 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Characterization of pore size distributions on carbonaceous adsorbents by DFT. Carbon (1999);37(8):1257-1264. 349 | P a g e Appendix A Appendix A A.1 Gas adsorption isotherms Gas adsorption is a prominent method to obtain a comprehensive characterization of porous materials with respect to the specific surface area, pore size distribution and porosity. Adsorption by mesopores is dominated by capillary condensation, whereas filling of micropores is controlled by stronger interactions between the adsorbate molecules and pore walls. It is worthwhile to note that this nomenclature address pore width but not pore shape. Figure A-1 shows adsorption of the gas with increasing gas pressure on a surface. Figure A-1: A schematic showing the adsorption of gas molecules on a material with increasing gas pressure (Adopted from Micromeretics Instrument Corporation). 350 | P a g e Appendix A The IUPAC classification of adsorption isotherms is illustrated in Figure A-2 [274]. The six types of isotherm are characteristic of adsorbents that are microporous (type I), nonporous or macroporous (types II, III, and VI) or mesoporous (types IV and V). Figure A-2: IUPAC classification of adsorption isotherms. It is generally accepted that the desorption isotherm is more appropriate than the adsorption isotherm for evaluating the pore size distribution of an adsorbent. This is because the desorption branch of the isotherm for the same volume of gas exhibits a lower relative pressure, hence resulting in a lower free energy state. Thus, the desorption isotherm is closer to the true thermodynamic stability. 351 | P a g e Appendix A A.2 Mesopore analysis – Barrett-Joyner-Halenda (BJH) method Mesopore size calculations are made assuming cylindrical pore geometry using the Kelvin equation in the following form: 𝑟𝑘 = −2𝛾𝑉𝑚 𝑅𝑇𝑙𝑛� 𝑃 � 𝑃𝑜 (A-1) Where γ = the surface tension of nitrogen at its boiling point (8.85 ergs/cm2 at 77 K) Vm = the molar volume of liquid nitrogen (34.7 cm3/mol) R = Gas constant (8.314 x 107 ergs/deg/mol) T = boiling point of nitrogen (77 K) P/Po = relative pressure of nitrogen rk = Kelvin radius of the pore Substituting the appropriate constants for nitrogen, equation (A-1) reduces to: 𝑡�Å� = 4.15 𝑃 log( 𝑜 ) (A-2) 𝑃 The Kelvin radius, rk is the radius of the pore in which condensation occurs at a relative pressure of P/Po. Since some adsorption has taken place on the walls of the pore prior to condensation, rk does not truly represent the actual pore radius. On the other hand, an adsorbed layer remains on the walls during evaporation in the desorption process. Hence, the actual pore radius rp is given by: 𝑟𝑝 = 𝑟𝑘 + 𝑡 (A-3) where t is the thickness of the adsorbed layer. This statistical t can be taken as 3.54 (Vads/Vm) since the thickness of one nitrogen molecular layer is 3.54 Å and Vads/Vm is the ratio of the volume of nitrogen 352 | P a g e Appendix A adsorbed at a given relative pressure to the volume adsorbed at the completion of a monolayer for a nonporous solid of the same composition as the porous sample. A more convenient method for estimating t was proposed by de Boer: 13.99 ) 𝑃 log� 𝑜 �+0.034 𝑡�Å� = �( (A-4) 𝑃 With this fundamental, the BJH method further assumes that the initial relative pressure (P/Po) is close to unity when all pores are filled with liquid and that the largest pore of radius rp1 has a physically adsorbed layer of nitrogen molecules of thickness t1. Inside this thickness is an inner capillary with radius rk from which evaporation takes places as P/Po is lowered. Hence, the relationship between the pore volume Vp1 and the inner capillary (Kelvin) volume Vk is established: 𝑉𝑝1 = 𝑉𝐾1 𝑟𝑝1 (A-5) 𝑟𝐾1 When the relative pressure is lowered from (P/Po)1 to (P/Po)2, a volume V1 will desorb from the surface. This liquid volume V1 represents not only emptying of the largest pore of its condensate but also a reduction in the thickness of its physically adsorbed layer by an amount ∆t1. Across this relative pressure decrease, the average change in thickness is ∆t1/2 and the pore volume of the largest pore may now be expressed as: 𝑉𝑝1 = 𝑉1 (𝑟 𝑟𝑝𝑙 𝐾1 +∆𝑡1 /2 )2 (A-6) When the relative pressure is again lowered to (P/Po)3, the volume of liquid desorbed includes not only the condensate from the next larger pore size, but also the volume from a second thinning of the physically adsorbed layer left behind in the pores of the largest size. The volume Vp2 desorbed from the pores of the smaller size is then given by: 353 | P a g e Appendix A 𝑉𝑝2 = � 𝑟𝑝2 𝑟𝐾1 + ∆𝑡1 � �𝑉2 − 𝑉∆𝑡2 � (A-7) An expression for V∆t2 can be written as: 𝑉∆𝑡2 = ∆𝑡2 𝐴𝑐1 (A-8) where Ac1 is the area exposed by the previously emptied pores from the physically adsorbed gas is desorbed. Equation (9) can be generalized to represent any step during the desorption process. Expressing this as a summation of the average area in unfilled pores down to, but not including, the pore that was emptied in the desorption, a general equation can be written: 𝑉∆𝑡𝑛 = ∆𝑡𝑛 ∑𝑛−1 𝑗=1 𝐴𝑐𝑗 (A-9) Assuming cylindrical pore geometry, the area of each pore, Ap can be calculated from the pore volume, 𝐴𝑝 = 2𝑉𝑝 (A-10) 𝑟𝑝 The pore size distribution can be then expressed as: 𝑉𝑝𝑛 = ( 𝑟𝑝𝑚 ∆𝑡 ) (∆𝑉𝑛 𝑟𝐾𝑛 + 𝑛 − ∆𝑡𝑛 ∑𝑛−1 𝑗=1 𝐴𝑐𝑗 ) (A-11) The total pore areas can then be obtained by the summation of Ap for each step in the desorption process. The BJH method computes the summation of Acj from Ap for each relative pressure decrement as follows; it is assumed that all the pores which emptied their condensate during a relative pressure decrement have an average radius rp. From the Kelvin radii at the upper and lower values of P/Po in the desorption step, the average capillary (core) radius is expressed as: 𝑟̅𝑐 = 𝑟̅𝑝 − 𝑡𝑟 (A-12) 354 | P a g e Appendix A where tr is the thickness of the adsorbed layer at the average radius in the interval in the current pressure decrement and is calculated from equation (2). The term “c” in equation (10) is given by: 𝑐= 𝑟̅𝑐 𝑟̅𝑝 = 𝑟̅𝑝 −𝑡�𝑟 (A-13) 𝑟̅𝑝 Equation (12) now can be used in conjunction with equation (14) as an exact expression for the computation of pore size distributions. A.3 Micropore analysis – Horvath and Kawazoe (HK) method Several approaches for micropore analysis have been used; for example, alpha-s method, MP method, HK method, DR method. However, while no single treatment is applicable to all situations, enough flexibility is provided in each to adequately describe a micropore system. In this thesis, the HK method is employed due to its suitability for carbon material. This method enables the calculation of pore size distribution of micropores from the low relative pressure region of the adsorption isotherm and is derived independently from the Kelvin equation. The expression of the adsorption potential function within slit-like micropores as a function of the effective pore width is as follows: 𝑃 𝑃𝑜 𝑅𝑇𝑙𝑛 � � = 𝐾 𝑁𝑠 𝐴𝑆 +𝑁𝐴 𝐴𝐴 𝜎4 𝑥 � 𝑑 𝜎 (𝑙+𝑑) 3(𝑙− )3 − 𝜎 10 𝑑 9(𝑙− )9 − 𝜎4 𝑑 3( )3 + 𝜎 10 𝑑 9( )9 � (A-14) where K = Avogadro’s number Ns = number of atoms per unit area of adsorbent As = 6𝑚𝑐 𝛼𝑠 𝛼𝐴 𝛼𝑠 𝛼𝐴 + 𝜒𝑠 𝜒𝐴 NA = number of molecules per unit area of adsorbate m = mass of an electron 355 | P a g e Appendix A c = speed of light αs = polarizability of adsorbent αA = polarizability of adsorbate χs = magnetic susceptibility of adsorbent χA = magnetic susceptibility of adsorbate AA = 3𝑚𝑐 𝛼𝐴 𝜒𝐴 (l – ds) = effective pore width where d = ds + dA and, ds and dA are the diameters of the adsorbent and adsorbate molecules respectively. l = the distance between two layers of adsorbent σ = 0.858d/2 A.4 Meso/Micropore analysis – Density Functional Theory (DFT) method Classical macroscopic approach such as BJH method and semi-empirical approach such as Horvath and Kawazoe (HK) not give a realistic description of the filling of micropores and even narrow mesopores, leading to an underestimation of pore sizes. To achieve a more realistic description microscopic theory which describes the sorption and phase behavior fluids in narrow pores on a molecular level, the density functional theory (DFT) method, in particular, the non-local the density functional theory (NLDFT) method is used. The NLDFT method correctly describe the local fluid structure near curved solid walls and the adsorption isotherms in model pores are determined based on the intermolecular potentials of the fluid-fluid and solid-fluid interactions. The relation between isotherms determined by these microscopic approaches and the experimental isotherm on a porous solid can be interpreted in terms of a Generalized Adsorption Isotherm (GAI) equation: 𝑃 𝑃𝑜 𝑊 𝑃 𝑃𝑜 𝑁 � � = ∫𝑊 𝑀𝐴𝑋 𝑁 � , 𝑊� 𝑓(𝑊)𝑑𝑊 𝑀𝐼𝑁 (A-15) 356 | P a g e Appendix A where N(P/Po) = Experimental adsorption isotherm data W = pore width N(P/Po,W) = Isotherm on a single pore of width W f(W) = the pore size distribution function. The GAI equation reflects the assumption that the total isotherm consists of a number of individual “single pore” isotherms multiplied by their relative distribution, f(W), over a range of pore sizes. The set of N(P/Po,W) isotherms is obtained by the DFT simulation while the pore size distribution is derived by solving the GAI equation numerically via a fast non-negative least square algorithm. A.5 Mercury porosimetry Porosimetry is an analytical technique used to determine various quantifiable aspects of a material's porous nature, such as pore diameter, total pore volume, surface area, and bulk and absolute densities. It is a relatively rapid method whereby a wide range of pore diameter (3 nm - 200 µm) and variety of porosity parameters can be determined. This technique involves the intrusion of mercury, a non-wetting liquid, at high pressure into a material through the use of a porosimeter. The pore size is then determined based on the external pressure needed to force the liquid into a pore against the opposing force of the liquid’s surface tension. The force balance equation known as Washburn’s equation, which is based on the capillary law governing liquid penetration into small spaces and the assumption that the material contains cylindrical pores, is given as: 𝑃𝐿 − 𝑃𝐺 = 4𝜎𝑐𝑜𝑠𝜃 𝐷𝑃 (A-16) where PL = pressure of liquid 357 | P a g e Appendix A PG = pressure of gas σ = surface tension of liquid (For mercury, σ = 480 mNm-1) θ = contact angle of intrusion liquid (For mercury, θ = 140°) DP = pore diameter As the pressure increases during an analysis, pore size is calculated for each pressure point and the corresponding volume of mercury required to fill these pores is measured. These measurements taken over a range of pressures give the pore volume versus pore size distribution for the sample material. The analysis usually will include the decreasing pressure portion, whereby the extrusion of the mercury is examined and calculated by the Washburn equation (Equation A-16). Extrusion P-V curves usually differs from intrusion curves because of mercury entrapment and because there is no driving force to bring the mercury out of the pores during the extrusion phase of the analysis. Differences between intrusion curves and extrusion curves can be used to characterize channel restrictions and the structure or shape of pores. Pore diameters may be offset toward larger values on extrusion curves because receding contact angles are smaller than advancing contact angles. This results in equivalent volumes of mercury extruding at lower pressures than those at which the pores were intruded. Also, pore irregularities, such as enlarged chambers and “ink-well” structures sometimes trap mercury. Total pore volume (Vtot) is determined based on the total intruded volume of mercury at the highest pressure determined. Total pore surface area (S) is calculated by: 𝑆= 𝑉 ∫ 𝑡𝑜𝑡 𝑝 𝛾|𝑐𝑜𝑠𝜃| 𝑑𝑉 (A-17) Total pore surface area is the area above the intrusion curve, and it is thus modeless and independent of the geometrical pore shape. Furthermore, the mean pore diameter (dmean) is calculated based on an assumption of cylindrical shape of pores open at ends: 358 | P a g e Appendix A 𝑑𝑚𝑒𝑎𝑛 = 4𝑉𝑡𝑜𝑡 𝑆 (A-18) Median pore diameter (dmedian) is the pore diameter at which 50% of the total intruded volume of mercury is intruded into the sample. In general, mean pore diameter emphasizes the smaller pores rather more than median pore diameter. The volume pore size distribution, Dv(d), is defined as the pore volume per unit interval of pore diameter (d) and based on a model of cylindrical pores, it can be expressed as: 𝐷𝑣 (𝑑) = 𝑝 𝑑𝑉 𝑑 𝑑𝑝 (A-19) 359 | P a g e List of Publications and Conferences List of Publications and Conferences International Journal Papers X. Chen, L. Hong, et al, “Evolution of Throttle-Channel Dual Pores in YSZ Ceramic Monolith through in-situ Grown Nano Carbon Wedges”, Journal of the European Ceramic Society, Volume: 32, Issue: 14, Pages: 3709-3722, Nov 2012. X. Chen, L. Hong, et al, “Ceramic Pore-Channels with Inducted Carbon-nanotubes for Removing Oil from Water”, Applied Materials and Interfaces, Volume: 4, Issue:4, Pages:1909-1918, Apr 2012. X. Chen, L. Hong, et al., “Aliphatic chain grafted polypyrrole as a precursor of carbon membrane”, Journal of Membrane Science, Volume: 379, Issue: 1-2, Pages: 353-360, Sep 2011 X. Chen, X.H. Tai and L. Hong, “Submicron-Scale Exclusion via Polymerizing an Aromatic Nylon in Molded Ceramic Monolith for Paving Interconnected Pore Channels”, Journal of the American Ceramic Society, Volume: 94, Issue: 2, Pages: 382-390, Feb 2011 X. Chen and L. Hong, “An In Situ Approach to Create Porous Ceramic Membrane: Polymerization of Acrylamide in a Confined Environment”, Journal of the American Ceramic Society, Vol. 93, Issue: 1, Pages: 96-103, Jan 2010 Industrial Property Rights X. Chen and L. Hong, “Fabrication of Porous Ceramic Matrix Shaped by In-Situ Growth of Nylon Nano Crystallites”, US Patent Application No.: PCT/SG2011/000230, Date Filed: 30 June 2010 X. Chen and L. Hong, “A Ceramic Membrane Containing Carbon Nanotubes”, US Patent Application No.: PCT/SG2012/000331, Date Filed: 12 September 2012 X. Chen and L. Hong, “Carbon Membrane derived from Grafted Double Polymer Layers”, Submitted for patent application. 360 | P a g e List of Publications and Conferences Conferences X. Chen and L. Hong, “In-situ polymerization of an organic monomer in a ceramic green object – to create interconnecting micro-pore channels.” MRS 2009 Spring Meeting in 2009, San Francisco, US, Oral Presentation. X. Chen and L. Hong, “Piercing interconnected pore channels by in-situ polymerization and graphitization in a molded ceramic monolith”, 3rd International Congress on Ceramics (ICC3) in 2010, Osaka, Japan, Oral Presentation. X. Chen and L. Hong, “Nano-porous ceramic filters prepared by in-situ pore-forming and interstitial constricting technique”, International Conference on Materials for Advanced Technologies (ICMAT 2011) in 2011, Singapore, Oral Presentation. X. Chen and L. Hong, “Structural and performance evolution of carbon membrane from grafted polypyrrole”, International Congress on Membranes and Membrane Processes (ICOM 2011) in 2011, Amsterdam, Netherlands, Oral Presentation. X. Chen and L. Hong, “Growth of carbon nanotube net on a porous ceramic membrane with well-defined throats for oily water treatment”, International Congress on Membranes and Membrane Processes (ICOM 2011) in 2011, Amsterdam, Netherlands, Poster Presentation. X. Chen and L. Hong, “Carbon-nanotubes Functionalized Ceramic Pore-Channels for Purification of Oily Water”, HOPE meeting in 2012, Tsukuba, Japan, Poster Presentation X. Chen and L. Hong, “Tapping the potential of Carbon Nano Tubes implanted in Ceramic Pore Channels for Oily Water Treatment”, 4th International Congress on Ceramics (ICC4) in 2012, Chicago, US, Interactive Poster Presentation X. Chen and L. Hong, “Carbon membrane derived from interfacial charged-grafted double polymer layers for gas separation”, EuroMembrane 2012 in 2012, London, UK, Oral Presentation X. Chen and L. Hong, “Unleashing the potential of carbon-nanotubes for removing oil from water: their deployment in pore channels of ceramic membrane”, EuroMembrane 2012 in 2012, London, UK, Poster Presentation 361 | P a g e [...]... micrographs of the cross-sections of YSZ membrane, in which the growth of CNTs was conducted at various temperatures as specified 161 Figure 7-6: TEM micrographs (a) Network of CNTs formed surrounding a ceramic particle, (b) A close-up view of a single strand of CNT 163 Figure 7-7: The variations of rejection to oil of an o/w emulsion of a membrane with the time of separation: (♦) Porous YSZ ceramic. .. properties of H2, N2, CO2 and CH4 through the carbon membranes revealed dense layer of carbon The transition of the doped pyrrole to carbon matrix was studied and understood through IR, XPS, 13 C-NMR and DSC characterization Finally, carbon nanotubes were introduced as structural pillars to relieve the thermal stress experienced during high pyrolysis temperature (>700 °C), ensuring the study of carbon. .. (between 2 to 50 nm) and finally, to micro- pore (50 nm) to meso-pores (between 2 to. .. of molecular weight of gas molecules 269 Figure 12-1: Schematic of ideology of charged-grafted double layer 274 Figure 12-2: FESEM micrographs of (a) the surface of a macro- porous ceramic pellet without zirconium gel layer; (b) the surface of zirconium gel layer on a macro porous ceramic pellet, which the insect is the cross-sectional image 276 Figure 12-3: Schematic of hierarchy porosity... the membrane and precipitation with calcium chloride solution Alumina pans; heating rate of 10 °C/min 145 Figure 7-1: Schematic of oil and grease removal technologies based on size of removable particles 150 Figure 7-2: Ideology of oil capture mechanism by carbon nano-tubes grown in pore channels of a porous ceramic membrane The pore size distribution of the porous ceramic membrane . MACRO TO MICRO POROUS CERAMIC AND CARBON MEDIA – PHILOSOPHY OF DESIGN AND FABRICATION CHEN XINWEI B. Eng. (Hons.), NUS A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF. 9.3.2 Grafting of linear segment to polypyrrole 214 9.3.3 Fabrication of carbon membrane on a porous ceramic substrate 217 9.3.4 Achieving meso -porous carbon membrane: sealing of pinholes 220. philosophy in designing porous structure in inorganic medium ranging across the full dimensions of pore sizes: from macro- pores (>50 nm) to meso-pores (between 2 to 50 nm) and finally, to